Structural arrangement and method for counteracting a vertical moment of a strut-braced wing

Abstract

An aircraft includes a fuselage and a pair of wings. Each wing is coupled to the fuselage at a wing-fuselage joint, and is supported by a strut coupled to the fuselage at a strut-fuselage joint and coupled to the wing at a strut-wing joint. The strut-fuselage joint is located below and at least partially aft of the wing-fuselage joint. The wing generates a lifting force when air passes over the wing. The lifting force induces a vertical moment about the wing-fuselage joint due to the location of the strut-fuselage joint below and at least partially aft of the wing-fuselage joint. The wing and/or the strut has a structural arrangement configured to counteract the vertical moment.

What is claimed is: 
     
       1. An aircraft, comprising:
 a fuselage; 
 a wing coupled to the fuselage at a wing-fuselage joint; 
 a strut coupled to the fuselage at a strut-fuselage joint and coupled to the wing at a strut-wing joint, the strut-fuselage joint located below and at least partially aft of the wing-fuselage joint; 
 wherein:
 the wing generates a lifting force when air passes over the wing; 
 the lifting force induces a vertical moment about the wing-fuselage joint due to the location of the strut-fuselage joint below and at least partially aft of the wing-fuselage joint; 
 the strut comprises an A-frame structure configured to counteract at least a portion of the vertical moment, the A-frame structure comprising a strut front spar and a strut rear spar each having a strut spar inboard end and a strut spar outboard end; 
 the strut spar inboard ends are spaced apart from each other at the strut-fuselage joint; and 
 the strut front spar and the strut rear spar having strut axes that converge to a point at the strut-wing joint where the strut spar outboard ends are coupled to the wing. 
 
 
     
     
       2. The aircraft of  claim 1 , wherein:
 the wing and the strut are each configured to counteract a portion of the vertical moment; and 
 a combination of the vertical moment counteracted by the wing, and the vertical moment counteracted by the strut, is equivalent to a total magnitude of the vertical moment. 
 
     
     
       3. The aircraft of  claim 1 , wherein:
 the strut front spar and the strut rear spar are respectively configured to carry tension load and compression load in response to the vertical moment induced by the lifting force; and 
 the strut spar inboard ends are configured to transfer the tension load and the compression load into the fuselage at a strut front attach point and a strut rear attach point of the strut-fuselage joint. 
 
     
     
       4. The aircraft of  claim 3 , wherein:
 the A-frame structure has an inboard end connector interconnecting the strut spar inboard ends; 
 the inboard end connector is configured to transfer shear load into the fuselage at the strut front attach point and the strut rear attach point; and 
 the shear load is in response to the tension load and the compression load respectively carried by the strut front spar and the strut rear spar. 
 
     
     
       5. The aircraft of  claim 3 , wherein:
 the strut includes a strut leading edge and a strut trailing edge, each extending from a strut root at the strut-fuselage joint, to a strut outboard end at the strut-wing joint; 
 the strut leading edge and the strut trailing edge define a tapered shape of the strut from the strut root to the strut outboard end; and 
 the tapered shape of the strut is complementary to a shape of the A-frame structure defined by the strut front spar and the strut rear spar. 
 
     
     
       6. The aircraft of  claim 3 , wherein:
 the strut includes a strut leading edge and a strut trailing edge, each extending from a strut root at the strut-fuselage joint, to a strut outboard end at the strut-wing joint;
 the strut front attach point is located forward of the strut spar inboard end of the strut front spar, and aft of the strut leading edge; and 
 the strut rear attach point is located aft of the strut spar inboard end of the strut rear spar, and forward of the strut trailing edge. 
 
 
     
     
       7. The aircraft of  claim 3 , wherein:
 the strut front spar and the strut rear spar are each contiguous, and each has a kink dividing the strut front spar and the strut rear spar into a strut spar inboard section and a strut spar outboard section; and 
 the strut spar inboard section of the strut front spar is angled forwardly relative to the strut spar outboard section of the strut front spar, and the strut spar inboard section of the strut rear spar is angled aftwardly relative to the strut spar outboard section of the strut front spar, to thereby increase the distance between the strut spar inboard ends. 
 
     
     
       8. The aircraft of  claim 7 , further comprising at least one of:
 a kink connector beam extending between and interconnecting the kinks respectively of the strut front spar and the strut rear spar; 
 a kink plate extending between and interconnecting the strut spar inboard section of the strut front spar to the strut spar inboard section of the strut rear spar; and 
 a pair of diagonal members, each extending from one of the strut spar inboard ends of one of the strut spars, to the kink of the other strut spar. 
 
     
     
       9. The aircraft of  claim 3 , further comprising:
 a strut front fitting extending forward of, and coupled to, the strut front spar, and configured to distribute the tension load into the fuselage at the strut front attach point of the strut-fuselage joint; and 
 a strut rear fitting extending aft of, and coupled to, the strut rear spar, and configured to distribute the compression load into the fuselage at the strut rear attach point of the strut-fuselage joint. 
 
     
     
       10. The aircraft of  claim 3 , wherein:
 the strut spar inboard end of the strut front spar and of the strut rear spar each has a spar slot extending along a neutral axis; 
 the A-frame structure including:
 a lug plate insertable within the spar slot in the strut front spar and the strut rear spar, the lug plate interconnecting the strut front spar and the strut rear spar, and extending forward of the strut front spar, and aft of the strut rear spar; 
 a plurality of strut lugs extending in an inboard direction from the lug plate, including one or more strut lugs located forward of the strut spar inboard end of the strut front spar, and one or more strut lugs located aft of the strut spar inboard end of the strut rear spar; and 
 
 the fuselage has a plurality of fuselage lugs protruding in an outboard direction for rotatably coupling, via one or more pins, to the strut lugs at the strut front attach point and the strut rear attach point. 
 
     
     
       11. The aircraft of  claim 3 , wherein:
 the strut outboard ends of the strut front spar and the strut rear spar respectively have a front spar plate and a rear spar plate, each extending in an outboard direction and overlapping each other and coupled together via mechanical fasteners; 
 at least one of the front spar plate and the rear spar plate has one or more strut lugs protruding in an outboard direction; 
 the wing has one or more wing lugs protruding from the wing in an inboard direction and configured complementary to the strut lugs; 
 the strut lugs and the wing lugs are rotatably coupled via a pin; 
 at least one of the spar front plate and the spar rear plate is coupled to the wing via at least one drag link oriented in a forward-aft direction and coupled to at least one of the spar front plate and the spar rear plate; and 
 the coupling of the front spar plate to the rear spar plate resolving the tension load and compression load respectively in the strut front spar and strut rear spar into axial tension in the wing lugs, and axial compression and axial tension respectively in the front drag link and the rear drag link. 
 
     
     
       12. An aircraft, comprising:
 a fuselage; 
 a wing coupled to the fuselage at a wing-fuselage joint, and having a wing trailing edge; 
 a strut coupled to the fuselage at a strut-fuselage joint and coupled to the wing at a strut-wing joint, the strut-fuselage joint located below and at least partially aft of the wing-fuselage joint, the strut has a strut leading edge, a portion of which is located aft of the wing trailing edge when the aircraft is viewed from a top-down perspective; 
 wherein:
 the wing generates a lifting force when air passes over the wing; 
 the lifting force induces a vertical moment about the wing-fuselage joint due to the location of the strut-fuselage joint below and at least partially aft of the wing-fuselage joint; 
 the strut comprises an A-frame structure configured to counteract at least a portion of the vertical moment, the A-frame structure comprising a strut front spar and a strut rear spar each having a strut spar inboard end and a strut spar outboard end; 
 
 the strut spar inboard ends are spaced apart from each other at the strut-fuselage joint; and 
 the strut front spar and the strut rear spar having strut axes that converge to a point at the strut-wing joint where the strut spar outboard ends are coupled to the wing. 
 
     
     
       13. A method of enhancing the performance of an aircraft, comprising:
 generating, using a wing, a lifting force when air passes over the wing, the wing is coupled to a fuselage at a wing-fuselage joint, and is supported by a strut coupled to the fuselage at a strut-fuselage joint located below and at least partially aft of the wing-fuselage joint, the strut comprises an A-frame structure having a strut front spar and a strut rear spar each having a strut spar inboard end and a strut spar outboard end, the strut spar inboard ends are spaced apart from each other at the strut-fuselage joint, the strut front spar and the strut rear spar having strut axes that converge to a point at the strut-wing joint where the strut spar outboard ends are coupled to the wing; 
 inducing a vertical moment about the wing-fuselage joint in response to the lifting force; and 
 counteracting at least a portion of the vertical moment using the strut. 
 
     
     
       14. The method of  claim 13 , wherein counteracting the vertical moment comprises:
 counteracting a portion of the vertical moment using a structural arrangement of the wing, and counteracting a portion of the vertical moment using a structural arrangement of the strut, a combination of the vertical moment counteracted by the wing and the vertical moment counteracted by the strut is equivalent to a total magnitude of the vertical moment. 
 
     
     
       15. The method of  claim 13 , wherein counteracting the vertical moment comprises:
 carrying tension load and compression load respectively in the strut front spar and the strut rear spar of the A-frame structure of the strut; and 
 transferring the tension load and the compression load into the fuselage at a strut front attach point and a strut rear attach point of the strut-fuselage joint. 
 
     
     
       16. The method of  claim 15 , further comprising:
 reacting shear load at the strut-fuselage joint using an inboard end connector interconnecting the strut spar inboard ends, the shear load resulting from the tension load and the compression load in the strut front spar and the strut rear spar. 
 
     
     
       17. The method of  claim 15 , wherein carrying the tension load and carrying the compression load comprises:
 carrying the tension load and the compression load respectively in the strut front spar and the strut rear spar, the strut having a strut leading edge and a strut trailing edge, each extending from a strut root at the strut-fuselage joint, to a strut outboard end at the strut-wing joint; and 
 wherein the strut leading edge and the strut trailing edge define a tapered shape of the strut from the strut root to the strut outboard end, the tapered shape is complementary to the A-frame structure defined by the strut front spar and the strut rear spar. 
 
     
     
       18. The method of  claim 15 , wherein carrying the tension load and carrying the compression load respectively comprises:
 carrying the tension load and the compression load respectively in the strut front spar and the strut rear spar, each of which is contiguous, and each has a kink dividing the strut front spar and the strut rear spar into a strut spar inboard section and a strut spar outboard section; and 
 wherein the strut spar inboard section of the strut front spar is angled forwardly relative to the strut spar outboard section of the strut front spar, and the strut spar inboard section of the strut rear spar is angled aftwardly relative to the strut spar outboard section of the strut front spar, to thereby increase the distance between the strut spar inboard ends. 
 
     
     
       19. The method of  claim 15 , further comprising:
 distributing the tension load into the strut front attach point using a strut front fitting extending forward of, and coupled to, the strut front spar; and 
 distributing the compression load into the strut rear attach point using a strut rear fitting extending aft of, and coupled to, the strut rear spar. 
 
     
     
       20. The method of  claim 15 , further comprising:
 distributing the tension load into the strut front attach point, and distributing the compression load into the strut rear attach point, using a lug plate insertable within a spar slot in the strut front spar and the strut rear spar, the lug plate interconnecting the strut front spar and the strut rear spar, and extending forward of the strut front spar, and aft of the strut rear spar; and 
 the lug plate having one or more strut lugs located forward of the strut front spar, and one or more strut lugs located aft of the strut rear spar, the strut lugs rotatably coupled via one or more pins to a plurality of fuselage lugs protruding from the fuselage at the strut front attach point and the strut rear attach point. 
 
     
     
       21. The method of  claim 15 , further comprising transferring the tension load and transferring the compression load into the wing at the strut-wing joint, by performing the following:
 transferring the tension load and the compression load respectively into a front spar plate and a rear spar plate respectively extending from the strut front spar and the strut rear spar, the front spar plate and rear spar plate are coupled together in overlapping relation, and at least one of the front spar plate and rear spar plate has a plurality of strut lugs protruding in an outboard direction; 
 resolving, via the front spar plate and the rear spar plate, the tension load and the compression load into:
 axial tension in a plurality of wing lugs protruding in an inboard direction and rotatably coupled to the plurality of strut lugs via a pin; and 
 axial compression and axial tension respectively in a front drag link and a rear drag link each extending in a forward-aft direction from at least one of the spar front plate and the spar rear plate.